TORONTO (miningweekly.com) – Canadian miner and project developer McEwen Mining has lifted the National Instrument 43-101-compliant inferred resource at its fully owned Los Azules copper project, in Argentina’s San Juan province, by 29% to 13.95-billion pounds.

However, the contained copper in the indicated resource decreased slightly to 4.45-billion pounds.

The company on Tuesday said the expanded resource incorporated 6 966 m of new drilling from ten additional holes. The resource remains open laterally, to depth and along strike.

The company said the Los Azules project is a unique asset in terms of size and grade for McEwen Mining. “This year's exploration drilling has demonstrated that there is significant potential to expand the resource well beyond our previous understanding of the deposit," chief owner Rob McEwen said in a statement.

This season was the first time a meaningful amount of deeper drilling was undertaken at Los Azules, with stronger machines moved to the site.

The deeper drilling had begun to identify a potential parallel trend, west of the original Los Azules orebody. Copper mineralisation discovered within this trend occurs near surface and also at depth, down to 1 050 m below surface.

As a result, many new exploration targets have emerged.

McEwen Mining on Tuesday said it had begun work on an updated preliminary economic assessment (PEA), which is expected to be complete in the third quarter of this year.

The updated PEA would be based on a significantly larger mineral resource and will evaluate the possibility of increasing the daily throughput. The PEA would also incorporate further metallurgical studies currently being done on the possibility of producing copper cathode instead of a concentrate and processing low-grade mineralised material not previously considered, through a heap leach.

The advantage of producing a copper cathode is that it would eliminate the contemplated slurry pipeline through Chile and would reduce Argentina's export tax on concentrate.

Los Azules is one of the world's largest, highest grade, undeveloped copper/porphyry deposits not owned by a major base-metals company, and is located in western San Juan, within a belt of porphyry copper deposits that straddle the Chile/Argentina border.

This belt contains some of the world's largest copper deposits, including Codelco's El Teniente and Andina mines, Anglo American's Los Bronces mine, Antofagasta's Los Pelambres mine and Xstrata's El Pachon project, among others.

McEwen Mining’s New York-listed shares have declined in value by 22.47% since the start of this year, and on Wednesday traded at $3.05 apiece.